The risk of multiple sclerosis in the U.S.A. in relation to sociogeographic features: a factor-analytic study.

The multiple sclerosis (MS) case-control ratio by state originating from the U.S. veteran series from World War II (Kurtzke Neurology 1979; 29: 1228-1235) was geographically compared with 46 sociogeographic variables from the period 1935-1958. Latitude was, by far, the variable most closely associated with MS in univariate testing. Multivariate analysis by factor analysis revealed that the MS rate was associated with 2 independent settings ("factors"). The first one was defined mainly socioeconomically and was characterized by indicators of higher affluence; better nutrition with a higher meat consumption in particular, and a higher sanitary level were the prominent features. The second MS-related bundle comprised characteristics of a colder climate along with further dietary variables (i.e. a diet low in fish and high in dairy products). The findings suggest a possible interaction of both socioeconomic and geoclimatic features in the etiology of MS; sanitation, diet and climate being of particular interest.